Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$168.57	8.621%	$183.1024	$183.10	$183.10	$183.10
Purchase #2	$100.41	11.231%	$111.687	$111.69	$111.70	$111.70
Purchase #3	$196.35	11.745%	$219.4113	$219.41	$219.40	$219.40
Purchase #4	$244.55	8.134%	$264.4417	$264.44	$264.45	$264.40
Purchase #5	$241.43	13.575%	$274.2041	$274.20	$274.20	$274.20
Purchase #6	$181.95	9.617%	$199.4481	$199.45	$199.45	$199.40
Purchase #7	$131.95	5.453%	$139.1452	$139.15	$139.15	$139.10
7 purchase totals =	$1,265.21		$1,391.4398	$1,391.44	$1,391.45	$1,391.30